Relationship Between Root Chemical Signals and Grain Quality of Rice

This study was designed to elucidate the relationship between root chemical signals and the quality of rice. Various ricegenotypes were used. Zeatin (Z) + zeatin riboside (ZR), abscisic acid (ABA), 1-aminocylopropane -1-carboxylic acid(ACC), and organic acids in roots during grain filling and the appearance quality, cooking/eating quality were investigated.The correlations among them were analyzed. The results showed that Z + ZR concentrations in the roots at mid- and late-grain-filling stages were significantly and positively correlated with the gel consistency and alkali spreading value (r =0.72* - 0.90**), whereas negatively correlated with the amylose content (r = -0.68* - -0.78**). ABA concentrations in rootsat mid- grain-filling stage were significantly and negatively correlated with the gel consistency and alkali spreading value(r = -0.90** - -0.91**), and positively correlated with the amylose content (r = 0.87**). ACC concentrations in root exudatesat mid-grain-filling stage were very significantly correlated with the percentage of chalky grains and chalkiness (r = 0.97**- 0.98**), and those at late-grain-filling stage were significantly correlated with chalkiness and chalky size (r = 0.69* -0.96**). The more the malic acid and succinic acid exuded from roots for a cultivar, the greater the breakdown values andthe smaller the setback values in the starch profile, and the results were reversed for a cultivar with more tartaric acid andcitric acid exuded from roots during the grain-filling period. The cultivar with more lactic acid in exudates had smaller gelconsistency and alkali spreading values, but had greater amylose content. When roots were treated with exogenous ZR,ABA, and ACC during grain filling, effects of the chemicals on the rice quality were consistent with the relationships ofthe endogenous hormones (Z + ZR, ABA, and ACC) with the quality indexes. Using rape cake as organic fertilizer canincrease the concentrations of malic acid and succinic acids exuded from roots as well as the breakdown value in starchprofile and reduce the setback value. The results suggest that root chemical signals play important roles in the formationof rice quality, and rice quality could be improved through regulating the signals.